Aerodynamics

• Upright handlebars place a cyclist's torso perpendicular to the ground, positioning the person's weight on the buttocks. The torso's upright position may be more natural for a casual cyclist, but it makes for the least possible stream-lined shape. The cyclist's torso creates wind resistance that is not created when using flat- or drop-style handlebars that allow a cyclist to lean forward, creating less contact area with the wind. The effects of this extra wind resistance are especially pronounced when pedaling into the wind or going downhill.
  
  

Weight Distribution

• Upright handlebars place a cyclist upright so that the person's weight is centered over the bicycle's seat tube. This position does not allow the cyclist to shift weight forward and backward over the wheels, limiting the ability to efficiently move a bike over obstacles or change the cornering characteristics of the bicycle. The upright position also limits how much a cyclist can use abdominal strength to help jump the bike or make subtle body changes for leaning into a corner.
  
  

Pedaling

• The cyclist can increase pedaling efficiency by leaning down in a more aerodynamic position. Flat and drop handlebars allow for the cyclist to get down in the lowest positions, moving the torso parallel with the ground and allowing the legs to deliver the most force to the cranks. The upright position does not allow for the leverage provided by this position and reduces the power delivered to the wheels.
  
  

Hand Positions

• Upright handlebars provide one hand position. This is fine for short rides, but for long distance cycling, a cyclist often will use multiple hand positions to reduce arm and hand fatigue. Hill climbs present a situation in which cyclists will want to position themselves forward, and upright handlebars do not allow for extensions or maneuverability. Drop bars feature multiple locations for the hands, while flat bars offer the ability to add bar ends that are easily accessible for extra leverage and positioning.